A standard blister package is comprised of a base foil having one or more upwardly open pockets each holding one or more items, e.g. pills, and a cover foil sealed atop the cover foil all around each of the pockets. Such packages are produced in high volume and at high speed in a continuous process where, in spite of the high production rate, it is essential that the cover foil be hermetically sealed completely around each pocket.
Such a production line has supply rolls that feed the cover foil and the support foil through several upstream treatment stations, namely a heater and a shaper for forming blisters or pockets in the support foil and a filler for putting the product into the pockets. A downstream sealer as for example described in U.S. Pat. No. 4,167,092 bonds the cover foil atop the base foil so that in a downstream stamper the bonded together cover foil and support foils can be subdivided into individual packages. According to actual application the format with respect to length and width dimension of the foil in the sealer varies, with an irregular sealing pattern with large sizes that not only is difficult to see, but that also makes it hard to seal uniformly with the considerable disadvantage that pharmaceutical products are not packed accurately.